Many computing systems, in particular mobile systems, have stacked processor and memory integrated circuit (IC) dies. For small form factor mobile systems, the stacking of IC dies helps to reduce the overall size of the system. In high performance systems, stacking IC dies using high density interconnect packaging techniques, such as through-silicon-via (TSV), can improve system bandwidth between processor and memory IC dies.
To date, the most widely used stacked packaging solutions utilize wire-bond technology to connect stacked IC dies or stacked packages, where connections between IC dies are made at the periphery of the stacked dies or packages. Emerging packaging alternatives, such as through-silicon-via (TSV) or chip-on-chip (COC), allow for connections between stacked IC dies using a two dimensional area array of connection sites.
COC packaging can be attractive when a single IC die is stacked on top of a processor IC die. TSV packaging is attractive when more than one IC die needs to be stacked on top of a processor IC die. One challenge with these approaches is the problem of matching up the connection sites between the wide variety of memory and processor IC die sizes.
One known solution involves using an interposer substrate to connect the processor IC die to the memory IC die. The interposer substrate reroutes signals to accommodate differences in the connection site placement between the two IC dies. Using an interposer substrate adds material and design cost, as well as complexity to the production flow, and is therefore undesirable.
A through-silicon-via (TSV) is an electrical connection that passes completely through an integrated circuit die from one surface of the die to the opposite surface of the die. “Silicon” in “through-silicon-via” does not limit the material of the integrated circuit die to silicon. The integrated circuit die may be a die of another semiconductor material. A TSV is typically a hole that extends through an integrated circuit die and is subsequently filled with electrically-conductive material to form the electrical connection. Two or more integrated circuit dies can be stacked on top on one another and connected together using through-silicon-vias (TSVs). The TSVs in adjacent integrated circuit dies can be connected together using, for example, solder bumps.
Individual integrated circuit dies that are stacked and connected together using TSVs are typically housed in a single package rather than being housed in separate packages. Because the integrated circuit dies are housed in a single package, they occupy less space than integrated circuit dies that are packaged separately and connected together through a printed circuit board (PCB). TSVs can also significantly reduce the amount and length of wiring that is used to connect together multiple integrated circuit dies, because the connections between the integrated circuit dies do not need to be routed through packages or a PCB. The shorter wires reduce power consumption and increase the performance of the integrated circuits.
In order for two integrated circuit dies to be connected together through TSVs, the TSVs need to have the same connection array structure in each integrated circuit die. Using the same TSV array structure in two integrated circuit dies allows corresponding TSVs in each die to be aligned when the two dies are stacked so that the TSVs can be connected using, e.g., solder bumps. This constraint limits the selection of integrated circuit dies that can be connected together using TSVs.
A processor IC die may be produced in multiple different die sizes as the design of the processor is shrunk due to a die shrink or a manufacturing process change. A processor IC die may need to attach to a variety of memory IC dies that are made by different manufacturers, have different capacities, and/or have different designs. If the dimensions of one of the integrated circuit dies is reduced, the TSVs in the two integrated circuit dies are no longer aligned when the integrated circuit dies are stacked and the TSVs cannot be connected together.